Thinking further about a "hot war" with Iran, what would that look like? Day 1: we sink their navy, and any of their air force that takes of is eliminated. Then what? If we don't invade, not much is going to happen. They have a sizeable army, but it would be useless if we don't put boots on the ground (which we shouldn't). How do you envision it?

The obvious answer is to have Iranian and Iraqi forces move on the U.S. military presence in Iraq and Kuwait. We've got about ~3K troops in Iraq and more than ~10K in Kuwait. That's actually our largest troop presence in the region, and so Iran's first military objective would be to attack all US forces in those two areas. If we obliterate their Navy (killing several thousand Iranian servicemen - these ships aren't empty), that's an act of complete war. Tehran will have little choice but to try to respond in similar fashion. They can't defeat the U.S. military, but they're going to have to engage. So they go into Kuwait, and maybe Saudi Arabia - to force the U.S. to engage them with land troops.

Another likely - but less certain - response would be to pull the trigger on Israel as well. No more sparse and isolated rocket attacks from Hizbollah; just have them start attacking en masse, and accept the Israeli response. This is to keep Israel focused on its own security, rather than attacking targets that the US doesn't want to be directly involved in.

Also likely is a call for help. China and Russia are not going to cede control over the area to the U.S. - Iran is an important client and a strategic check on US/Western interests in the region. They obviously don't want any direct engagement, but neither are they going to leave Iran out to dry. They'll provide replacement aircraft, and possibly small naval craft - and China may actually move some of their ships into Iranian ports to keep the US from attacking again.

All quite devastating to the international shipping that the US is ostensibly trying to protect. Which is the problem with a disproportional response - it's disproportional. Yes, the US could blow up the stability of the entire Middle East in order to hinder these rocket attacks. But then the US has to face the consequences of doing that.